THE BIOSPHERE

1. THE BIOSPHERE • Objectives • Define and explain the important terms • Understand the main influences leading to plant and animal distributions • Describe and explain the main characteristics of the major global biomes • Explain some of the factors leading to change in these regions

2. Introduction • The biosphere is the biologically inhabited portion of the Earth in which ecosystems operate • Studies of the biosphere are linked with geology, ecology, soils, atmospheric processes and climate, oceans • Humans influence the biosphere through a range of deliberate and inadvertent practices • Biomes are major global scale zones with characteristic life forms of plants and animals

3. Figure 8.1

4. Functions and processes within the biosphere: characteristics • The biosphere is characterized by its dynamism • Boundaries within the biosphere result from a range of factors • Often along environmental gradients • Often not a sudden change but transitional areas (ecotones) • Each region of the biosphere has distinctive energy flows, biomass, trophic levels, nutrient cycling

5. Functions and processes within the biosphere: controlling factors • Temperature regime • Actual temperature and seasonal pattern is critical for life • Growing season creates a base-line of food for others • Adaptability to temperature ranges • Moisture availability • Local rainfall regime – esp. length of dry season • Potential evapotranspiration and accessibility to river/groundwater • Zonal factors • Regional macroclimate (equatorial, monsoonal etc) correlate to biomes • Creates favourable/unfavourable conditions for life • Azonal factors • Disrupt otherwise climatically-controlled pattern • Geomorphology affects drainage and aspect. • Geology

6. Functions and processes controlling the biosphere: The major biogeographic realms • Biogeographical realms are divided into zones/biomes • Classification of realms • Holarctic (from Laurasia) – Palaearictic (Eurasia) and Nearctic (N America Greenland) • Palaeotropic (from Gondwanaland) – southern continents; Afrotropical, Indian, Indomalaysian , Neotropical, Australia, Antarctic realms • Usually ignores the oceanic realms • Classification helps in taxonomy • Past climatic and tectonic changes are vital to today’s patterns

7. Figure 8.2

8. TROPICAL BIOMES

9. Figure 8.3

10. Equatorial and tropical forests • Climate • mean annual temp ~25o with little seasonal variation • 2000mm rainfall/yr – dry season no longer than 5 months • Further from equator = increased seasonality • Soils • high rates of biogeochemical activity • Infertile soils, lack of recently weathered rock – oxisols • Fertility is dependent on continual leaf litter • Soil type changes with variability in seasonality • High net primary productivity • 40% global terrestrial productivity • Degree of seasonality has a large impact on primary productivit

11. …cont • Rainforest vegetation • Broad leaved evergreens dominate in a closed canopy • Competition for light causes stratification of canopies and epiphytes and lianas (adaptive) • Distinctive tree types within each stratum • Adaptations for light, surplus water removal , phanerophytes • Characteristics between realms remain similar but actual species vary - e.g. dipterocarps (Indian) vs legumes (S American) • Rainforest animals • Animal species often restrict their range to a single stratum • Animal adaptations (prehensile tails, fruit eating birds) • Lack of under-storey vegetation allows space for large ground dwelling animals – wind pigs, jaguars, large rodents

12. Figure 8.4 Source: From Schultz, 1995, after Leith, 1964

15. Figure 8.5 Source: Photo courtesy of Sandra Patino

16. Figure 8.6 Source:Jerry Young/Dorling Kindersley

17. Figure 8.7 Source:Dorling Kindersley

18. …cont • Regeneration • When natural clearings appear due to fire, wind or water species compete for the new niche (especially light) • Soil erosion and nutrient loss at a minimal • Mimicked by humans in shifting cultivation • Complexity • Associations of vegetation rather than domination by single species • High species diversity probably due to complex structure, length of time since major climatic disturbance • Local specific azonal factors cause high diversity – e.g. slope, local geology, drainage • Historical shifts between savanna and forest

19. Savanna • Climate • Temperature is similar to rainforest but a longer dry season • Dr season = >250mm/month for > 5 months • Gradient from the equator • Savanna woodland → tree savanna → shrub savanna → savanna grassland • Soil = one of the major controls • Most found on continental shields – ancient infertile soil • Ecosystem change • Easily influenced by human activities and major climatic readjustment e.g. Quaternary

20. Figure 8.10 Source: After Whittaker, 1975

21. …cont • Vegetation • More open canopy than forests: few trees except near water table • Mosaic – diversity of structure due to differences in water and soil nutrients availability • ‘Fire season’ – allows fruiting and nutrient supply • Xeromorphic adaptations and Rhizomes • Grassland stands dominated by few species • Animals • Large numbers of herbivores (esp. Central and East Africa) • Large animal predators occupy wooded areas of shelter, preying on herbivores • Adaptations – nocturnalism to reduce water loss and migration to track seasonally available food

22. Deserts • Climate = dominant control (hot and dry all yr) • Insufficient moisture for complete ground cover • Large diurnal temp fluctuations • Some areas = regular but insufficient rain to counteract evaporation • Some areas = no sporadic rainfall for years • Soils • Poorly developed but increased nutrients around roots • Basic ecology • Vegetation = varied but low in height and very open stands • Clustering dependent on water, local geology, geomorphology • Biomass is mainly underground – geophytes or therophytes • Low biodiversity • Net primary productivity is strongly related to rainfall

23. Figure 8.12 Source:Photo courtesy of John Coleman

24. …cont • Adaptations • Plant and animal adaptations to control evaporation and maximise water conservation (xeromorphic) • Plants adaptations • Control transpiration (nocturnal stomatal opening) • Woodiness prevents wilting • Lengthy dormant season • Annual plants – dependent on rainfall season • Animal adaptations • Physiological - surface area/body mass ratio, sweat control etc • Behavioural – nocturnal, dormancy, cryptozoic

25. TEMPERATE BIOMES

26. Figure 8.13

27. Mediterranean/Chaparral Biome • Transition between desert and true temperate biomes • Climate • Warm all yr round with low rainfall, summer drought • Soil • Regardless of parent material the upper soil becomes very dry in summer – evaporites can develop • Vegetation • Tendency for xerophytic scrubland with strongly developed adaptations against natural fires • Thick, smooth bark, deep roots • Crytophytes – bulbs, rhizomes • Distinctive post-fire regeneration cycle exists • Animals adapt to avoid drought and fire stresses e.g. burrowing

28. …cont • Mediterranean - once sclerophyllous mixed woodland - now dominated by maquis due to human impact • Scrubland, canopy may reach 3m (gorse, broom, olive etc) • Garrigue vegetation where less water (evergreen, more sparse) • Chaparral (N. America) - sclerophyllous • Thick bark, fore resistant (Eriodictyon tomentosum) • Deer, elk and grizzly bear • ‘soft chaparral’ near coast • S African Mediterranean has distinctive flora • Where temperate forest remains it is simpler than in the N Hemisphere • Southern Cape Province – coniferous Podocarpus understorey • Australia – mallee scrublands • Eucalyptus species with acacia understorey, marsupial grazers

29. Figure 8.14

30. Temperate grasslands • Continental interior of the Holarctic and eastern region of the Netropical • Climate – annual precn <500mm, long dry season • Continental convection rainfall in summer, snowfall in winter • Geomorphological and glacial heritage • Gently undulating areas with rich soils – agriculture e.g. US Prairies • Vegetation • Dominated by grasslands, usually perennial and xerophyllous • Adaptations to maximise effectiveness of precn and minimise fire damage • E.g. shallow, turf forming dense roots • Animals - originally large herds of herbivores • Lack of cover had caused development of speed, bulk or burrowing habits for protection • Reduced or extinct due to humans e.g. passenger pigeons of N America • Verv extensive human impacts

31. Figure 8.16 Source: After Walter 1990

32. Temperature deciduous forest • Only in N Hemisphere • Climate • Moist but temperate all yr, a few months above 10oC • Soils • Brown earth molisols – rich soil fauna and nutrients • Under conifers soils become leached – podzols – heathland results • Ecology • Mainly deciduous trees, some epiphytes • Four layers (canopy, shrub layer, field layer, ground layer) – dependent on species comprising the canopy • Very marked seasonality of vegetation - creates succession of dominants • Flowering trees and plants – assists wind pollination • Animals may hibernate and burrow to avoid winter effects • MASSIVE HUMAN IMPACTS– reduced coverage and species

33. Figure 8.17 Source:Photo courtesy of Joseph Holden

34. Southern hemisphere, evergreen temperate forest • Variant of temperate deciduous forest biome • S Hemisphere equivalent – later development of deciduous habitat in N Hemisphere after continental split • Ecology • Usually 2 tree canopies and a shrub layer • Climbers and epiphytes • Less frequently a ground flora • Southern Beech and podocarp family are important • Rich bird life exp New Zealand • e.g. meat eating parrots

35. THE COLD BIOMES

36. Figure 8.18

37. Taiga • Lack of any extensive Taiga in the S Hemisphere • Climate • Cool all year and little rainfall (mostly continental interiors) • Extending poleward from < 5 months > 10oC to 1 month • Very limited growing season • Soil • Usually a podzol • Slow nutrient cycles, large accumulated litter layer, strong layering • Peat bogs develop where glacial effects impede soil drainage

38. Taiga ecology • Wide ecotone between temperate and boreal forest mosaics • depends on local conditions e,g, soil type • Warmer and wetter taiga • unbroken forest stands • True central taiga • more discontinuous, greater dominance of ground layer – lichens • Dominant Species • Eurasian forests dominated by Norway spruce and Scots pine • American forest dominated by lodgepole pine and alpine fur • Adaptations - maximise growing season and utilise poor soils • increased stored sugar concentration in winter • fan shaped roots • Animals • Adapted to conditions e.g. migration, fur

39. Figure 8.19 Source: Photo courtesy of Ed Reschke/Peter Arnold Inc/Still Pictures

40. Tundra • Most challenging environments for plants and animals • Climate • Equator limit = 10oC for the warmest month • Winter may plunge to -50oC • Strong, dry, cold winds prevalent, snow accumulates • Lowland areas characterised by continuous permafrost • Warmer in coastal regions • Soils (cryosols) • Litter layer of partly decomposed, highly acidic plant matter • Gleyed horizon overlies permanently frozen layer • Geomorphology– very strong immediate influence • Glacial erosion and current fluvial activity caused shallow soils • Underlying sands and gravels left in valley floors – causes veg mosaic

41. Figure 8.20

42. Figure 8.21

43. …cont • Vegetation • Limited floristically because Quaternary destroyed the biome • 3 fold structure –low shrub, tussocky grasses, mosses/ lichens • Becomes more simple the more extreme the conditions • Slow growth • Most are perrenial • Adapted to reproduction in very short growing season e.g. bulbs • Grasses and sedges dominate and dwarf trees e.g. Betula nana • Health dominates on coarser substrate – Erica families • Animals • Migrating animals – causes interesting population dynamics • Low productivity requires large areas to support migrating herds e,g, reindeer • Hibernation, burrowing an insulating fur/feathers • Convergent evolution – very similar habit and structure across all realms

44. Mountain biomes • Topography plays a local role in altering regional biome patterns • Mountains form barriers to dispersal of life forms • Mountains often have unique biome characteristics and gradients • Aspect - impacts on local scale biodiversity • Local land use patterns change in mountain areas • Case study – Andes mountain biome • Lower slope = tierra templada • tropical pre-mountain forest • Middle slopes – upper tierra templada/lower tierra fria • temperate rain or cloud forest • Upper slopes = Tierra fria and tierra helada • above treeline species are xerophytic with giant forms of plants due to reduced oxygen and increased UV radiation

45. Figure 8.22 Source: After Breckle, 2002

46. Figure 8.23 Source: Photo courtesy of Julia Edwards

47. Changing biomes • Despite specific characteristics (functional or structural) – all biomes are very dynamic in nature • Natural changes have always occurred however human intervention is now increasingly important • anthropogenic climate change • intensified resource utilisation • Introductions of alien species – altering local balances • Approaches to resource utilisation are changing – as reflected in the popularity of venues such as the Eden project • Ho resilient is the biosphere in response to human and natural agents of change? • History suggests a large capacity to accommodate vast climatic changes • However gaps exist in our knowledge • Need management

48. Figure 8.24 Source: After Whittaker, 1975

49. Summary • Themes for drawing geographical comparisons between biomes • Climate, soil, wildlife types, adaptations • Local human factors also alter biomes • Ecotones • Tropical biomes - forests, savanna, desert • Temperature biomes – forest, grasslands • Cold biomes – taiga, tundra